They are not going to let Bernie win. The DNC biggest hurdle is doing it in such a way that his army of morons won’t realize they got screwed...again.
There is no way to do that.
The socialists have been organizing and planning since just after the 2016 Democrat convention. Many of them assumed at that point that even if Bernie had seventy five percent of the vote the Democrat party would still strip the nomination away.
They will run their own candidate.